The prior art is already aware of screwdrivers which transmit and measure various amounts of torque. They employ springs through which the torque is transmitted from a screwdriver handle to the screw and by virtue of inducing tension in the spring when the handle is turned against resistance from the driven screw. A scale reveals the torque.
Because of the inherent resilience in the torquing spring, it is important the assembly with the spring be of an optimum arrangement to assure repeated usefulness of the screwdriver and repeated accuracy of torque production.
The present invention achieves the aforementioned objectives by providing a screwdriver assembly wherein the spring and the mounting thereof result in providing accuracy in torque production. Further, the accuracy is achievable in repeated uses and over a range of applied torques.
Further, this invention provides the screwdriver with features mentioned above and it does so with a screwdriver handle which is ergonomically appealing in its fit with the hand of the user such that maximum torque can be exerted by the hand and onto the screwdriver handle. Also, the handle provides for forceful gripping, even if and when itinerant liquid is on the handle. The strength of the spring, that is its resistance to torquing, is selected to be compatible with the usual strength of an ordinary user's hand.
Still further, the screwdriver of this invention is fluid-tightly sealed to preclude the entry of fluids into the interior of the screwdriver handle, and thus the screwdriver maintains its accuracy and sterility for use in the medical field, such as in applications relative to bone screws.
Additionally, the screwdriver of this invention is assembled in a manner to avoid disassembly, and thus there is no opportunity for tampering which can upset the sealed condition or the accuracy of the torque production.
Even moreso, the screwdriver of this invention is arranged for ready and accurate calibration and for limiting the amount of measurable torque transmitted and thereby avoid damage to the instrument.
Other objects and advantages will be apparent upon reading the following description in conjunction with the accompanying drawings.